This invention relates generally to forced-air heating, air conditioning and ventilating apparatus in which circulation air from a comfort space is treated and is supplied back to the comfort space. The invention is also directed to forced air systems which include a heat recovery ventilator.
Heat recovery ventilators have been introduced to improve the quality of air in air-tight homes. That is, in modern homes designed to minimize or eliminate air leakage or intrusion, there is very little leakage of air into or out of the house. This can result in the accumulation of stale air. For this reason the heat recovery ventilator or HRV is installed in the home to discharge stale air and replace it with fresh make-up air from outdoors. The HRV has a heat- or heat- and- moisture exchanger incorporated into it so that in winter the leaving air warms (or warms and moistens) the entering make-up air, and in the summer the leaving air cools or cools and dries the entering warm make-up air.
The HRV typically incorporates one or more blowers to cause a positive flow of the discharge air out and the make-up air in, and can be operated on its own wall control or else tied in with a furnace or central air conditioner to go on and off with the room air circulation blower.
A number of heat recovery ventilators have been proposed, and one typical version is shown in U.S. Pat. No. 5,138,098. The HRV is typically provided with its own internal ducting separate from the return and supply ducts of the forced air furnace, air conditioner or heat pump system.
While there are clear advantages to employing the same ductwork with both the heating and cooling system and with the HRV, in practice the two systems tend to interfere with one another.